An approach to analysis of dynamic crack growth at bimaterial interface

In this paper is presented the new approach to asymptotic analysis of the stress and strain fields around a crack tip that is propagating dynamically along a bimaterial interface. Through asymptotic analysis the problem is being reduced to solving the Riemann-Hilbert's problem, what yields the strain potential that is used for determination of the strain field around a crack tip. The considered field is that of a dynamically propagating crack with a speed that is between zero and shear wave speed of the less stiffer of the two materials, bound along the interface. Using the new approach in asymptotic analysis of the strain field around a tip of a dynamically propagating crack and possibilities offered by the Mathematica programming package, the results are obtained that are compared to both experimental and numerical results on the dynamic interfacial fracture known from the literature. This comparison showed that it is necessary to apply the complete expression obtained by asymptotic analysis of optical data and not only its first term as it was done in previous analyses

Correlation of serum concentration of 25-hydroxy vitamin D and bone density in fеmale population older than 35 years of age

SAŽETAK Uvod: Hipovitaminoza vitamina D je danas široko zastupljena u svetu, u svim starosnim grupama sa većom prevalencom kod žena, posebno kod žena sa osteopenijom i primarnom osteoporozom. Cilj ove studije jeste razvijanje populacionog farmakokinetičkog (PFK) modela klirensa 25-hidroksi vitamina D, identifikacija i kvantifikacija faktora koji ga određuju kod žena starijih od 35 godina, kao i ispitivanje korelacije serumskih 25-hidroksi vitamina D sa vrednostima mineralne gustine kostiju, godinama starosti, kvalitetom života, stepenom depresivnosti i prisustvom straha kod ispitanica. Ispitanici i Metode istraživanja: Studija je obuhvatila 224 žene starije od 35 godina, koje su dolazile na osteodenzitometrijiski pregled u Kliniči centar Kragujevac. Ispitavana populacija podeljena je u tri podgrupe: žene u premenopauzi (od 35. godine do menopauze), žene u peri i/ili postmenopauzi (od menopauze do 65. godine života) i starije žene (od 65. do 75. godine života). U PFK analizi korišćen je softverski program NONMEM (Non linear mixed effect model) i ADVAN 1 subrutina. Brojni demografski, klinički, biohemijski, hormonski i medikamentozni podaci su isptivani kao faktori varijabilnosti klirensa 25-hidroksi vitamina D u sve tri subpopulacije žena. Procena depresije, staha i kvaliteta života je vršena upotrebom validiranih i kulturološki adaptiranih upitnika. Rezultati: Dobijene se srednje, populacione vrednosti klirensa 25-hidroksi vitamina D, identifiokavani su i kvantifikovani faktori koji ga određuju, kao i vrednosti inter- i intraindividulane varijabilnosti u ispitivanim subpopulacijama. Za validaciju dobijenih PFK modela korišćena je eksterna validacija. Pokazano je postojanje korelacije između serumskih koncentracija 25-hidroksi vitamina D sa kvalitetom života kod žena sa redovnim menstrualnim ciklusom; mineralnom gustinom kostiju i vrednostima T skora dobijenih DXA metodom i kvalitetom života kod žena u postmenopauzi. Zaključak: Dobijene farmakokinetiče jednačine mogu se koristiti u donošenju preporuka za korigovanje i individulazaciju doze ovog vitamina u vidu suplementacije kod žena u Srbiji, u tri njihova značajna životna perioda.ABSTRACT Introduction: Hypovitaminosis of vitamin D is widely spread over the world, throughout every age group, but, dominantly present in female population with osteopenia and primary osteoporosis. The aim of this study was to develop a population pharmacokinetics (PFK) model of 25-hydroxy vitamin D clearance, identification and quantification of factors defining it in female's population older than 35 years, as well as to research the correlations between serum concentration of 25-hydroxy vitamin D and values of bone density, age, life quality, depression level and presence of fear among the study subjects. Patients and Methods: The study population consisted of 224 women older than 35 years, which were taking osteodensitometry tests in Clinical center in Kragujevac. Test population was divided into 3 subgroups: women in premenopause (from 35 years to menopause) and women in peri- and/or in postmenopause (between menopause and 65 years of age) and elderly women (from 65 to 75 years of age). For PFK analysis a NONMEM (Non linear mixed effect model) softwear was used as well as ADVAN 1 subroutine. Numerous demographic, clinical, biochemical, hormonal and medicamental data were investigated as factors of clearance variability of 25-hydroxy vitamin D for all three female subpopulations. Results: Middle values for population clearance of 25-hydroxy vitamin D were acquired, its defining factors were identified and quantified, as well as inter- and intraindividual variables for study population. For validation of acquired PFK models external validation was applied. Correlation between serum concentration of 25-hydroxy vitamin D and life quality for females with regular period, mineral bone density and values for T score from DXA method and life quality for females in postmenopause, was confirmed. Conclusion: Defined pharmacokinetic equations can be used for making recommendation, corrections and individualization of vitamin D doses, through supplementation, for women in Serbia, during their three most important life period

The analysis of the chromosomal aberrations frequency of the employees from different workplaces in the zone of ionizing radiation.

Cilj predstavljenog istraživanja je da ispita uticaj malih doza jonizujućeg zračenja na zaposlene na različitim radnim mestima u zoni jonizujućeg zračenja. Materijal i metode: Za studiju retrospektivne prirode analizirani su rezultati dobijeni iz kartona preventivno-periodičnih medicinskih pregleda 148 zaposlenih na različitim radnim mestima u zoni jonizujućeg zračenja u Kliničkom Centru Srbije a koji obavljaju preglede u Institutu za medicinu rada Srbije. Ispitanici su podeljeni u tri velike grupe u odnosu na izvor zračenja-oblast rada na zaposlene u nuklearnoj medicini, intrerventnoj radiologiji i opštoj radiologiji. Podaci korišćeni za studiju su podaci sa prethodnog/prvog periodičnog pregleda koji je obavljan pre ulaska u zonu jonizujućeg zračenja ili u toku prve godine izlaganja (u toku obavljanja specijalizacije, u skladu sa odlukom poslodavca da pošalje zaposlenog na pregled) i podaci sa poslednjeg periodičnog pregleda. Uzimani su u obzir ukupni i ekspozicioni radni staž, vrsta izvora zračenja, hematološki parametri (eritrociti, retikulociti, leukociti sa leukocitarnom formulom, trombociti), frekvenca i broj nestabilnih hromozomskih aberacija (ishod testa nestabilnih hromozomskih aberacija) kao i ishod mikronukleusnog testa i njihov broj (značajnih za ocenu radne sposobnosti), primljena kumulativna petogodišnja doza zračenja, morbiditet ispitanika i prisutvo profesionalnih bolesti. Hematološki parametri (eritrociti-Er, retikulociti-Rtc, ukupni leukociti-Leu, monociti-Mo, neutrofili-Neut, eozinofili-Eo, bazofili-Ba, limfociti-Ly i trombociti-Tr) su dobijani ispitivanjem periferne venske krvi u aparatu Beckman Coulter HMX ( na poslednjem periodičnom pregledu) a na prethodnom su uglavnom ispitivani starom metodom ručnog brojanja ćelija (preračunatih za statistički obradu). Nestabilne hromozomske aberacije su dobijane modifikovanom Moorhead’s mikro metodom. Mikronukleusni test je rađen metodom po Fenech-u i Morley-u...The aim of the research is to analyse the influence of the small doses of ionizing radiation on the employees from different workplaces in the zone of ionizing radiation. Material and methods: For this study of the retrospective nature we have analyzed results obtained from the medical records based on preventive-periodical examinations of 148 persons employed at different workplaces in the zone of ionizing radiation at the Clinical Center of the Republic of Serbia. All of the employees go to medical examinations at the Institute of Occupational Medicine of Serbia. The employees were divided into three large groups as related to the source of radiation – the field of work: the nuclear medicine employees, the interventional radiology employees and the general radiology employees. The data was taken from the previous/initial checkup which had been done before the entrance to the zone of ionizing radiation or during the first year of exposure to radiation (during the specialization period, in accordance with employer’s decision to send an employee to the examination) as well as the data from the last periodical examination. We also took into consideration total and exposition work periods, type of radiation source, haematological parameters (erythrocytes, reticulocytes, leukocytes with differential blood count, platelets), frequency and number of unstable chromosomal aberrations (the results of the test of the unstable chromosomal aberrations), the results of micronucleus test and their number (important for the assessment of working ability), as well as received cumulative five-year radiation dose, morbidity of patients and presence of occupational diseases. The hematological parameters (erythrocytes-RBC, reticulocytes-Rtc, total leucocytes- WBS, monocytes-Mo, neutrophils-Neu, eosinophils-Eo, basophils-Ba and platelets) were obtained through processing of the peripheral vein blood by Beckman Coulter HMX apparatus (at the periodical checkup), while at the previous / initial checkup it was done through the old method of manual cell counting (recalculated for statistical processing)..

Parenteral Lipid-Based Nanoparticles for CNS Disorders: Integrating Various Facets of Preclinical Evaluation towards More Effective Clinical Translation

Contemporary trends in combinatorial chemistry and the design of pharmaceuticals targeting brain disorders have favored the development of drug candidates with increased lipophilicity and poorer water solubility, with the expected improvement in delivery across the blood–brain barrier (BBB). The growing availability of innovative excipients/ligands allowing improved brain targeting and controlled drug release makes the lipid nanocarriers a reasonable choice to overcome the factors impeding drug delivery through the BBB. However, a wide variety of methods, study designs and experimental conditions utilized in the literature hinder their systematic comparison, and thus slows the advances in brain-targeting by lipid-based nanoparticles. This review provides an overview of the methods most commonly utilized during the preclinical testing of liposomes, nanoemulsions, solid lipid nanoparticles and nanostructured lipid carriers intended for the treatment of various CNS disorders via the parenteral route. In order to fully elucidate the structure, stability, safety profiles, biodistribution, metabolism, pharmacokinetics and immunological effects of such lipid-based nanoparticles, a transdisciplinary approach to preclinical characterization is mandatory, covering a comprehensive set of physical, chemical, in vitro and in vivo biological testing

A proposal of innovative injectability assessment method for intravenous formulations - case study on PEGylated nanoemulsions

1. INTRODUCTION Syringeability and injectability are recognised as fundamental performance parameters / critical quality attributes of any parenteral dosage form. Syringeability refers to the ability of an injectable preparation to transfer from a vial through a hypodermic needle prior an injection, while injectability is defined as the force, or pressure, required to inject the formulation from a syringe-needle system into the tissue [1]. When developing drug delivery systems, the priority is usually the release kinetics, biocompatibility or other factors that may come in conflict with the optimal parameters for the applicability of those systems [2]. The aim of this research was to develop a method that could be used for injectability assessment of the intravenous formulations and the application of this method on curcumin-loaded PEGylated nanoemulsions (NEs) in order to gage the impact of PEGylation on NEs injectability. 2. MATERIALS AND METHODS 2.1. Nanoemulsion preparation Nanoemulsions were prepared using high pressure homogenization method. The aqueous phase (glycerol, polysorbate 80, sodium oleate and highly purified water) was added into the oil phase (soybean oil, soybean lecithin, medium chain triglycerides, butylhydroxytoluene, benzyl alcohol, curcumin and PEGylated phospholipid – PEG2000-DSPE in 0.1 %, 0.3 % or 0.6 % concentrations) and mixed using rotor-stator homogenizer (IKA Ultra-Turrax® T25 digital, IKA®-Werke GmbH and Co. KG, Staufen, Germany), and further processed on high pressure homogenizer (EmulsiFlex-C3, Avestin Inc., Canada) at 800 bar for 10 discontinued cycles. The non PEGylated formulation was marked as CS, and the PEGylated ones were marked S1, S3 and S6, referring to the PEG2000-DSPE concentration. 2.2. Physicochemical characterization The NEs droplet size (Z-Ave) and droplet size distribution (PDI) were determined with Zetasizer Nano ZS90 (Malvern Instruments Ltd., Worcestershire). Rheological analysis was performed using MCR 302 air-bearing rheometer (Anton Paar, Graz, Austria) equipped with coaxial cylinders system (CC27 measuring bob with C-PTD 180/Air) with sheer rate range of 0.1-100 s-1 at 20°C. 2.3. Injectabilty assesment The injectability of the NEs was expressed as force (N) needed to extrude the NE in the function of the extruded volume (ml). About 10 ml of the NE was loaded into the 10 ml syringe and extruded through the 25 G scalp vein infusion set (Romed, Wilnis, Netherlands) into the blood mimicking solution, circulating through pump at 4 ml/min, in order to assess the NEs’ performance in the prospective intravenous administration. The NEs were extruded at 1 mm/s croshead speed of the loading cell of the texure analyzer (EZ-LX Compact Table-Top Testing Machine, Shimadzu, Japan) with the TrapeziumX software version 1.5 used for data collection and analysis 3. RESULTS AND DISCUSSION 3.1. Physicochemical characterization The NEs have average size of about 100 nm, with the PDI values below 0.20, indicating suitability for intravenous application. It could be observed from Fig. 1 that the addition of PEGylated phospholipids caused an increase in NE viscosity, as could be expected given that the polyethylene glycols are used in parenteral suspensions as stabilizing - rheology modifying agents [3]. 3.2. Injectability assessment The injectability assessment was performed with syringe-needle system used in our laboratory for intravenous administration in in vivo animal studies. As blood-mimicking solution, 36.6 %, v/v, glycerol solution was used [4]. It could be observed from Fig. 2 that the injectability of NEs depended on their viscosity, with the higher pressure needed to extrude the formulations with the higher PEG2000-DSPE concentration. Even though, to the best of our knowledge, there are no studies investigating the injectability of the intravenous preparations, based on some previous research on subcutaneous model [5], it is recommended the maximum force used to inject the formulations should be kept about 20 N, which would eliminate S3 and S6 from further investigation (Fig. 2). 4. CONCLUSION The injectability method used in this research proved as a useful tool in screening formulations adequate for prospective intravenous use. 5. REFERENCES 1. Cilurzo, F., et al. Injectability Evaluation: An Open Issue. AAPS PharmSciTech, 2011. 12(2): 604-609. 2. Sarmadi, M., et al. Modeling, design, and machine learning-based framework for optimal injectability of microparticle-based drug formulations. Science advances, 2020. 6: eabb6594. 3. Gullapalli, R. P., Mazzitelli, C. L. Polyethylene glycols in oral and parenteral formulations—A critical review. International Journal of Pharmaceutics, 2015. 496(2): 219-239. 4. Yousif, M. Y., et al.. Deriving a blood-mimicking fluid for particle image velocimetry in Sylgard-184 vascular models. In Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2009 (pp. 1412-1415 5. Watt, R. P., et al. (2019). Injectability as a function of viscosity and dosing materials for subcutaneous administration. International Journal of Pharmaceutics, 2019:554, 376-386. ACKNOWLEDGMENT This research was funded by the MESDT, Republic of Serbia through Grant Agreement with University of Belgrade-Faculty of Pharmacy No: 451-03-68/2022-14/200161 and supported by the Science Fund of the Republic of Serbia, GRANT No 7749108, Neuroimmune aspects of mood, anxiety and cognitive effects of leads/drug candidates acting at GABAA and/or sigma-2 receptors: In vitro/in vivo delineation by nano- and hiPSC-based platform - NanoCellEmоCog

Structural analysis of PEGylated nanoemulsions using EPR spectroscopy – the impact of an active compound incorporated in stabilizing layer

INTRODUCTION Nanoemulsions (NEs) offer a flexible platform for drug delivery via several administration routes. Rapid plasma clearance brought on by interactions with plasma proteins and the activation of the mononuclear phagocytic system is the greatest challenge NEs face after parenteral administration. PEGylation, or adding PEGylated phospholipids to the stabilizing layer of the NEs, is one method for ensuring that droplets circulate for a longer period of time. It is crucial to select the optimum concentration of the PEGylated in order to maintain the necessary physicochemical properties of NEs while providing appropriate surface coverage with the PEG chains. Curcumin is a model active that has been found to be localized in the stabilizing layer of NEs (1-3) and offers a wide range of potential health benefits, but due to its short plasma half-life, new strategies for enhancing bioavailability are required. The purpose of this study is to investigate the effects of various PEGylated phospholipid (PEG2000-DSPE) concentrations on the structural properties of NEs with an active placed in the stabilizing layer. PREPARATION OF NANOEMULSIONS All the NEs were prepared using the high pressure homogenization technique. The aqueous phase (glycerol, polysorbate 80, sodium oleate and highly purified water) was added to the oil phase (soybean oil, medium chain triglycerides, soybean lecithin, buthylhydroxytoluene, curcumin and 0.1%/0.3%/0.6% PEG2000-DSPE) and mixed at 11000rpm for 1 min on rotor stator homogenizer (IKA Ultra-Turrax T25 digital, IKA-Werke GmbH & Co. KG, Staufen, Germany), and then further processed at 800 bar for 10 discontinued cycles (EmulsiFlex-C3, Avestin Inc., Ottawa,ON, Canada) to obtain CS21, CS23 and CS26 formulations. NANOEMULSION DROPLET SIZE The droplet size was assessed through the dynamic light scattering method and presented as mean droplet size (Z-ave) and polydispersity index (PDI), after diluting the NEs 1:500 (v/v) in highly purified water. ELECTRON PARAMAGNETIC RESONANCE (EPR) SPECTROSCOPY For this study three amphiphilic fatty acid derivatives labeled at different positions of the aliphatic chain (5-DSA, 12-DSA and 16-DSA) were used to probe the dynamics of the membrane at different depths. Stock solutions of the spin probes were prepared in absolute ethanol at 1mM concentration. Subsequently, 15 µl of the stock solutions were evaporated and then incubated with 1 ml of the NE sample in final concentration of 0.015 mM. The resulting spectra was analyzed in terms of rotational correlation time (τR), order parameter (S) and isotropic hyperfine constant (αN). RESULTS AND DISCUSION All of the formulations had average droplet sizes between 95 and 103 nm and PDI values under 0.25, which indicated that they were suitable for parenteral administration. The results of the EPR investigation showed that the stabilizing layer changed as the amount of PEGylated phospholipids increased, indicating that the PEGylation threshold has not yet been reached in the stabilizing layer. The EPR research also showed that the 5-DSA spin probe's spectra were significantly affected by the addition of various PEGylated phospholipid concentrations (Figure 1). This indicates that the portion of the stabilizing layer nearest to the aqueous phase was the one most affected by the increase in the PEGylated phospholipid concentration. Table 1 provides the calculated values for the spectrum parameters. The mobility of the spin-probe and the time it takes for the spin-probe to make a full rotation is reflected in the τR parameter, which was changed the most, compared to the other parameters, by the variations in the PEGylated phospholipid content. A formulation with the most rigid stabilizing layer had the largest τR values, which, in this instance, was the formulation with 0.1% PEG2000-DSPE. It's interesting to note that the addition of PEGylated phospholipid had the opposite effect of strengthening the stabilizing layer. Further PEG2000-DSPE addition appeared to result in nanoemulsions with a less rigid stabilizing layer, possibly indicating that larger concentrations of the PEGylating agent lead to interface destabilization. The interactions between the curcumin, a symmetrical molecule with two aromatic ring systems and a bent conformation located in the stabilizing layer and the extra stabilizer are likely responsible for this. The other two spin probes (12-DSA and 16-DSA) provide information about the stabilizing layer located closer to the oil core. Based on the data provided in Table 1 it can be inferred that the PEGylation mostly affects the stabilizing layer's areas closest to the aqueous interface, leaving the parts closer to the oil core largely not impacted. CONCLUSION This study demonstrates that one of the key elements in assessing how PEGylation affects the NE system is the active's localization. To pick the concentration of the PEGylated phospholipid that will offer the best surface coverage without compromising the integrity of the interface, additional considerations must be addressed in the event of an active situated in the stabilizing layer. In this instance, it may be hypothesized that the lowest PEG2000-DSPE concentration of 0.1%, CS21, will produce NEs that can slow down curcumin release the most compared to the other two formulations. Additionally, given that further addition of the PEGylated phospholipid causes the formation of less rigid stabilizing layer, further inquiries should be made to see the impact of these changes on the interactions with plasma proteins and biological fate of the droplets upon administration

Analyzing the impact of the oil phase selection and curcumin presence on the nanoemulsion stabilizing layer using electron paramagnetic resonance spectroscopy

ANALYZING THE IMPACT OF THE OIL PHASE SELECTION AND CURCUMIN PRESENCE ON THE NANOEMULSION STABILIZING LAYER USING ELECTRON PARAMAGNETIC RESONANCE SPECTROSCOPY Jelena Đoković1*, Sotiria Demisli2, Vassiliki Papadimitriou2, Aristotelis Xenakis2, Snežana Savić1 1University of Belgrade – Faculty of Pharmacy, Department of Pharmaceutical Technology and Cosmetology, Belgrade, Serbia 2National Hellenic Research Foundation – Institute of Chemical Biology, Athens, Greece *[email protected] The stabilizing layer of nanoemulsions impacts their stability and destiny upon in vivo administration (1). The aim of this work was to gain information about the dynamics of the surfactants’ monolayer when different oils (soybean / fish) were used, and obtain data regarding the localization of curcumin (2), an active compound with many potential health benefits, using electron paramagnetic resonance (EPR) spectroscopy. Formulations were analysed using EPR technique with three different spin probes: 5-, 12- and 16-doxyl stearic acid (DSA), to investigate membrane dynamics at different depths. The results indicated that the oil type played a crucial role, not only on the structure, but also in the localization of the bioactive compound. The addition of curcumin changed the rotational correlation time (τR) values, most notably for 5-DSA, both in soybean oil and fish oil nanoemulsions, indicating its localization in the stabilizing layer, but with opposite effects. In the soybean oil nanoemulsion the addition of curcumin increased spin probe mobility, with τR decreasing from 2.18±0.60 ns to 1.66±0.61 ns, indicating a less rigid stabilizing structure, while in the fish oil formulations it resulted in a more rigid structure reflected in τR increase from 1.19±0.10 ns to 2.96±0.81 ns and 1.63±0.13 ns to 2.27±0.19 ns, for 5-DSA and 12-DSA, respectively. This study concluded that the curcumin is located in the stabilizing layer of nanoemulsions, but its impact on stabilizing layer structure depended on the oil phase selection, with particular stabilizing effects on fish oil nanoemulsions. References 1. Nikolic, I. et al. Curcumin-loaded low‐energy nanoemulsions: Linking EPR spectroscopy‐ analysed microstructure and antioxidant potential with in vitro evaluated biological activity. J. Mol. Liq. 2020, 301, 112479. 2. Griffith, O.H. and Jost, P.C. Lipid Spin Labels in Biological Membrane. In Spin Labeling, Theory and Applications; Berliner, L.J., Eds.; Academic Press: New York, NY, USA, 1976; pp 454–484 Acknowledgements This research was funded by the MESDT, Republic of Serbia through Grant Agreement with University of Belgrade – Faculty of Pharmacy No: 451-03-68/2022-14/200161 and supported by the Science Fund of the Republic of Serbia, GRANT No 7749108, Neuroimmune aspects of mood, anxiety and cognitive effects of leads/drug candidates acting at GABAA and/or sigma‐2 receptors: In vitro/in vivo delineation by nano‐ and hiPSC‐based platform - NanoCellEmоCo

Overcoming the low oral bioavailability of deuterated pyrazoloquinolinone ligand dk-i-60-3 by nanonization: A knowledge-based approach

Poor water solubility of new chemical entities is considered as one of the main obstacles in drug development, as it usually leads to low bioavailability after administration. To overcome these problems, the selection of the appropriate formulation technology needs to be based on the physicochemical properties of the drug and introduced in the early stages of drug research. One example of the new potential drug substance with poor solubility is DK-I-60-3, deuterated pyrazoloquinolinone, designed for the treatment of various neuropsychiatric disorders. In this research, based on preformulation studies, nanocrystal technology was chosen to improve the oral bioavailability of DK-I-60-3. Nanocrystal dispersions stabilized by sodium lauryl sulfate and polyvinylpyrrolidone were prepared by modified wet media milling technique, with the selection of appropriate process and formulation parameters. The nanoparticles characterization included particle size and zeta potential measurements, differential scanning calorimetry, X-ray powder diffraction, dissolution and solubility study, and in vivo pharmacokinetic experiments. Developed formulations had small uniform particle sizes and were stable for three months. Nanonization caused decreased crystallite size and induced crystal defects formation, as well as a DK-I-60-3 solubility increase. Furthermore, after oral administration of the developed formulations in rats, two to three-fold bioavailability enhancement was observed in plasma and investigated organs, including the brain